<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="./lib/vue.js"></script>
  </head>
  <body>
    <div id="app">
      <input
        type="text"
        name=""
        id=""
        v-bind:value="username"
        @input=" username= $event.target.value "
      />
      {{username}}
    </div>
    <script>
      var vm = new Vue({
        el: "#app",
        data() {
          return {
            username: "zhangsan",
          };
        },
        methods: {},
      });
    </script>
  </body>
</html>
